Telephone-circuit.



No. 669,7"), Patented Mar. l2, I90l. C. E. SCBIBNER.

TELEPHONE CIRCUIT. (Application filed Nov. 13, 1897. Renewed Sept. 4, 1900.)

(No Model.)

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ATENT Prion.

CHARLES E. SCRIBNER, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE WESTERN ELECTRIC COMPANY, OF SAME PLACE.

TELEPHONE-CIRCUIT.

SPECIFICATION forming part of Letters Patent No. 669,710. dated March 12, 1901.

Application filed November 18, 1897. Renewed September 4, 1900. Serial No. 28,973. (No model.)

To Ml whom it may concern:

Be it known that I, OHARLEsE. SCRIBNER,

a citizen of the United States, residing at Chicago, in the county of Cook and State of Illinois, have invented a certain new and useful Improvement in Telephone-Circuits, (Case No. 453,) of which the followingis a full, clear,

concise, and exact description, reference being had to the accompanying drawing, forming a part of this specification.

My invention concerns the operation of telephone transmitting instruments at substations by means of current supplied over the telephone line conductors from a central point, the windings of an induction-coil and an accumulator, such as a condenser or equivalent device, being associated by peculiar circuits with the transmitting telephone, whereby speech transmission of unusually high efticiency may be attained.

In the system of this invention I have dispensed with the impedancecoils formerly used in association with the transmittingtelephone to prevent the short-circuiting of incoming telephonic currents through the transmitter and have arranged the circuits so that there are no connections foreign to the transmitter-circuit in shunt about the telephone induction coil. In accordance with my invention a source of current is connected in a bridge of the telephone-circuit at the central office, and the line conductors at the substation are united by two bridges. One of the windings of an induction-coil is included in the undivided portion of the circuit, and the other winding is in one of the aforesaid bridges. The resistance-varying transmitter is included in one of the bridges, and an accumulator, such as a condenser or a polarization-battery, is included in the other bridge. Thereceiving-telephoneispreferably placed in the bridge which includes the accumulator, being thus in shunt of the transmitting-telephone. If the receiving-telephone were included serially in the line-circuit, the system would be operative; but the impedance and resistance of the receiving-telephone would decrease to some extent the efficiency in speech transmission.

The invention is illustrated in the attached drawing.

The drawing represents two telephone-lines, l 2 and 3 t, which are assumed to be connected in a complete circuit through the agency of link conductors in a telephoneswitchboard. In the switchboard, which is also a point from wnich the lines receive their current-supply for exciting the transmitting telephones, the line circuit is furnished with a bridge or cross conductor 5, which includes a souroeaof current, together with windings b and l) of impedance-coils for preventing the shunting of telephonic cur rent through the bridge.

The substation is equipped with a receiving-telephone c, a transmitting-telephone cl, an induction-coil e, having four windings, and a condenser f. The line-circuit may be considered as being complete through winding 6, transmittingtelephone (1, and winding (2 of the induction-coil. About the transmitting-telephone a shunt-circuit 6 is arranged, which includes serially a winding 6 of the induction-coil, the receiving-telephone c, the condeuserf, and the winding 6 of the induction-coil. 'lhe windings eand e should of course tend to magnetize the core in the same direction when traversed by current, and windings e and 6 should have similar relationstoeachother. WVindingsee shouldbeso related to windings e e that they tend to magnetize the core in the same direction if they were traversed serially by a continuous current. A steady current flows from batterya in the central office through both lines to the substations thereof, finding circuit at each substation through the winding e, transmittingtelephone cl, and the winding 6 of the induction-coil. An increase in the resistance of the transmittirig-telephone d at a station tends to diminish the current through the windings e and e and for an instant diverts the current through the shunt 6, which charges the condenser f. The current flowing through windings e and 6 1s then in proper direction to induce an electromotive force in windings e and c tending to still further diminish the current there. A subsequent decrease in the resistance of transmitter (1 permits an increased current to flow in the line-circuit, at the same time permitting the discharge of condenser f. This discharge takes place through windings e and e, in proper direction to accentuate the increased flow through windings 6 e Soundwaves striking the transmitter d therefore set up inthe line-circuit an undulating current, whose undulations are greatly amplified by the inductive action of the condenser f, acting through the windings e 6 The receiving-telephone 6 should have a resistance of about twenty-five ohms. When the receiver is of usual construction, the condenserf may be of two microfarads capacity, under which conditions the impedance of the receiving-telephone appears to have no deleterious efiect in the shunt-circuit.

Undulations created in the line-wires 1 2 are not propagated through the bridge 5 at the station of current-supply on account of the presence in the bridge of theimpedancecoils b b, but traverse the line conductors 3 and 4: to the distant station. This current is substantially an alternating current which finds free circuit through the condenser f and the receiving-telephone c.

The efficiency of the system in receiving telephonic currents is in no wise impaired by placing the receiver 0 in the shunt-circuit 6 instead of in the direct line-circuit, while the efficiency of transmission is greatly increased by eliminating the impedance of the receiver from 'the line-circuit, and the resistance of the circuitto the exciting-current is diminished. Polarization-cells used in place of condensers act in a similar manner except that with the condenser the counter-electromotive force is not limited, but may equal or excel the impressed electromotive force. While I have illustrated and described condensers f at the substations, it is evident that other counter-electromotive-force devices or accumulators, such as polarization-cells or resistance-coils, may be used in substantially the same way, although in some cases with inferior effioiency. I therefore do not wish to be understood as limiting my invention to its use with a condenser. 1

I claim as new and desire to secure by Letters Patent- 1. The combination with a telephone-line and means for supplying current in the line, of a transmitting-telephone and a winding of an induction-coil included seriallyin the line.- circuit, a shunt-circuit about the transmitting-telephone, and a receiving-telephone, a condenser and a second winding of the induction-coil all included serially in the said shunt-circuit, as described.

2. The combination with a telephone-line and a source of current in a bridge of the line, of a transmitting-telephone in a bridge of the line at the substation, an induction-coil having two windings in the said bridge with the transmitting-telephone, a shunt-circuit about the transmittingtelephone, two windings of the said induction-coil in the said shunt and adjacent to the different terminals of the transmitting-telephone, respectively, and a receiving-telephone and a condenserin circuit with said shunt between the said windings in the shunt, as described.

3. In a centralized-batterytelephone system, a main telephone-circuit and a source of transmitter-current supply included therein, combined at a substation with a telephonetransmitter,an induction-coil and an accumulator, such as a condenser, the said transmitter and the said accumulator being in parallel branches of the main circuit, the primary winding of the induction-coil being in one of said branches, and the secondary winding of said induction-coil being in the main circuit in series with the said parallel branches thereof.

4:. The combination in a main-line-battery telephone system, of a substation or local transmitting-circuit containing a telephonetransmitter, the primary winding of an induction-coil, and an accumulator,with a main telephone-circuit containing a common source of current-supply and the secondary winding of the said induction-coil, the substation ends of the said main circuit being connectedwith the opposite sides of the said local transmitter-circuit, the ends of said main'circuit being thus connected by two parallel paths, the transmitter being in one of said paths, and the accumulator in the other path.

5. The combination with a metallic telephone-circuit, and a source of current in a.

CHARLES E. SORIBNER.

Witnesses:

ELLA EDLER, FRANK MOBERTY. 

